Picture-transmitting system



Jan. 22, 1929. v

A. WEAVER ET AL PICTURE TRANSMITTING SYSTEM Filed March 26, 1924 m1 f TT [N VEN TORS L MTORNEY Patented Jan. 22, 1929.

UNITED STATES PATENT OFFICE.

ALLAN WEAVER,-OF BROOKLYN, NEW YORK, AND FRED R. MGMURRY, OF WESTWOOD, NEW JERSEY, ASSIGNORS TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY,

A CORPORATION OF NEW YORK.

PICTURE-TRANSMITTING SYSTEM.

Application filed March 26, 1924. Serial No. 702,084.

The principal object of our invent-ion is to provide new and improved apparatus for the electrical transmission of pictures. Another ob-ject of our invention is to provide means to adapt a picture transmitting system for operation according as the transmission is from a positive or a negative. Still another object of our invention is to provide for a simple adjustment of the circuits in a picture transmission system so that it can be changed readily to adapt it for transmission and Fig. 3 is a general symbolic diagram of the entire system. I

The glass drum 11 is rotated slowly on its axis and traversed lengthwise in the meantime, so that the spot underlying the opening in the screen 16 describes a helical course'relatively to the drum 11. Wrapped about the drum 11 is a picture representation in the form of a semi-transparent film 12. I The lamp 14 has its light focused by the lens 15 at the opening in the screen 16 and this light shines through the film 12 and the drum 11 on the photoelectric cell 13.

This cell 13 is in circuit with the battery 17 and according to well-known principles, the current in this circuit will vary in dependence on the light that passes through the spot of the film 12 to the cell 13.

The grid 18 of a three-electrode vacuum tube or audion has its circuit completed to the filament 20 through an adjustable portion of the resistance of the potentiometer P,, the entire resistance being comprised in the circuit of the photoelectric cell 13. The electromotive force normally applied to the grid 18 is determined by the potentiometer A the battery 21, the plate 19, the filament 20 v and the windings of three marginal relays A, B and C. These are adjusted so that for a certain small amount of light in the cell 13, none of them picks up; for a limited increase of the light, A only picks up; then with more light, A and B pick up; and with still more light, A, B and C pick up.

The armatures of the relays A, B and C control the circuits of the two selector magnets 1 and 2. For successive elements of the film 12, successive contacts are made at '29 by the wiper 28 which rotates with the drum 11. At each contact the circuit of the punch magnet 26 is closed and a transverse row of holes (more or less complete) is punched in the tape of Fig. 2, which holes are deter mined by the energization of the magnets 1 and 2. In Fig. 2, a solid black circle means a hole punched in the tape and an open circle merely indicates a position at which a hole might have been but was not punched.

It will be .seen that the circuit for the magnet 2 comprises a switch Z which may make connection either with the front contact X or the back contact Y of the relay B. As shown film 12 under the opening in the screen 16, increased transparency means lncrease of light on the cell 13 and increase of current in the marginal relays A, B and C, the following relations can readil be established from Fig. 1 as given in the ta le below:

Reproducing from nega- Reproducing from positive (Z on X) tive (Z on Y) Marginal relaysd M M operate ag- 2533? nets Code 332 nets Code selected selected None White '1 o Black-.... 1und2 o o Light gray None Dark gray 2 o A and B Dark gray 2 0 Light gray None A, B and C Black-.- 1and2 o 0 White 1 o For example, when reproducing from a negative, a picture shade of white means black in the negative and none of the marginal relays will'be operated and magnet 1 will be selected. On the other hand, when reproducing from a positive, a picture shade of black means black in the negative and with switch Z to the right, both magnet-s 1 and 2 will be energized. Similarly, the table can be followed through for the other combinations.

From the foregoing it will be seen that according as the film 12 is a negative or a positive, the system will be completely adapted by throwing the switch Z to the left or the right, respectively.

By the term picture representation we mean either a negative or a positive. If the picture representation is a negative, then light places therein correspond to dark places in the picture, and vice versa. If the picture representation is a positive, then light places therein correspond to light places in the picture, etc.

The tape produced by the apparatus of Fig 1 is fed to a tape transmitter TT as shown in Fig. 3. This device and the remaining elements of Fig. 3 here to be mentioned and all elements of text message printing telegraph apparatus and, therefore, they are represented only symbolically in Fig. 3 and are only described briefly here. The tape entering the tape transmitter TT causes code currents to be put on the line L. P is a printer at the sending station that prints the picture the same as it is printed at P at the receiving station. There the received code currents actuate a machine perforator MP which produces a tape similar to that at the sending station. This tape goes to the tape transmitter TT' whichdetermines the operation of the printer P, which prints a blank for white, a small dot forlight gray,

a medium dotfor dark gray and a heavy dot v for black. Thus the sheet produced by the printer P is a half-tone reproduction of the picture corresponding to the picture representation 12 at the sending end,

Special code combinations are punched in the tape and sent for carriage return and line sh ft when the edge of the picture repre-- sentation 12 passes the opening in the screen 16 in Fig. 1.

In the foregoing specification, the case has been considered more particularly in which the picture is to be received as a positive. If

it is desired to receive it as a negative, the proper adjustment of switch Z will be obvious. In general, when the transmitted picture representation and the received picture representation are to be alike, bot-h positives or bothnegatives, then switch Z should be on contact X, but when unlike, then on Y.

As an example of the utility of sending from a'positive, it may be desired to send from a sketch made witha black crayon on semi-transparent paper; such a sketch could be put directly on drum 11 in Fig. 1 and by putting switeh'Z on contact Y it would reproduce as a positive at the receiving end.

' We claim:

1. The combination in a picture transmission system of means for testing the lights and shades of the elemental areas of a picture representation, a line, a plurality of selective devices operable in accordance with said lights and shades for sending over said line a signaling current, means at the receiving end of the line responsive to said current for reproducing the picture, and means for altering the operation of said selective devices such that the character of the picture reproduction at the receiving end remains the same whether the representation at the sending end be positive or negativef 2. In combination, means to test successive elements of a picture representation for light or shade, marginal relays to be actuated accordingly, selector magnets with circuits comprising contacts of said marginal relays, and means to change said circuits to adapt the marginal relays to actuate the-proper selector magnets in accordance with whether the said picturerepresentation is a negative or a positive.

3. In combination, a light-sensitive element, marginal relays in which electric ouron said element, a source of light directed toward said element, means to interpose successive parts of a picture representation in the path of said light, selector magnets controlled by said marginal relays, and adjustable means to adapt the system according to whether the picture representation is a negative or a positive.

4. In combination, means to test successive elements of a picture representation for light or shade, marginal relays to be actuated accordingly, selector magnets with circuits comprising contacts of said marginal relays, and a switch to change -the connection for one of such circuits from a front contact to a back contact, or vice versa, whereby the combination of operated marginal relays will actuate the proper selector magnets in accordance with whether the said picture representation is a negative or a positive.

5. In combination, means to test successive elements of a picture representation for light I or shade, marginal relays to be actuated accordingly, a line, selector magnets, circuits including contacts of said marginal relays,

means controlled by said magnets to send ment, a source of light and means to direct it.

to said element, means to pass. the elements of a picture representation in succession across the path of the light from said source to said sensitive element, means including a marginally operated device to transmit electrical impulses determined by the lightfall ing on said sensitive element, and means to adjust the last mentioned means so that the electrical impulses will be the same for like picture elements whether the picture representation is a negative or a positive.

7. The combination in a picture. transmission system of means for testing the lights and shades of the elemental areas of a picture representation, a line, a transmitting device selectively operable in accordance with the tone value of an elemental area of the picture representation to send over the line a signaling current of a definite character,

means for altering said device whereby a current of the same definite character is also sent for a different tone value of a picture element, and means at the receiving end of the line responsive to said current for reproducinIg the picture.

a picture transmission system, means for testing the elemental tone values of a pic-' ture representation, a line, a tape perforator for punching in a tape combinations representing the tone values of said representation, means for sending over the line a signaling current varying in accordance with the punchings in said ta e, means at the receiving end of the line or reproducing the 9. In combination, means to test the elemental areas of a picture representation to determine the tone values thereof which may vary over a range of values, a plurality of selector magnets for producing code combinations in accordance with the tone'values of the picture, and means for controlling the production of said code combinations so that they correspond to the tone values of-the picture Whether the picture representation is a negative or a positive.

10. In combination, means to test successive elements of a picture representation for light or shade, a pluralityof devices to be selectively energized in accordance with the degree of light or shade of the successive elements of the picture, and means to control the energization of said devices so that they Will be energized the same for like elements of the picture whether the picture representation is a negative or a positive.

11. The combination in a picture transmission-system of means for testing the lights and shades of theelemental areas of a picture representation, a line, a marginal relay operable in accordance with said lights and shades for sending over said line a si naling .current, means at the receiving en of the line responsive to said current for reproducing the picture, and means for altering the operation of said relay such that the reproduction may be either positive or negative regardless of whether the picture representation at the transmitting end is positive or negative.

In testimony whereof, we have signedour names to this specification this 24th day of March, 1924.

, ALLAN WEAVER.

FRED R. MOMURRY. 

